1. Field of the Invention
The present invention relates to a two-wheel drive two-wheel vehicle, and more particularly a two-wheel drive bicycle having the rear wheel driven by the traditional chain or shaft mechanism and the front wheel driven by a series of shafts and gears transferring power from the driven rear wheel to the front wheel.
2. Description of the Related Art
As off road biking has gained broader appeal, the demands that riders place on their bicycles have increased dramatically. Downhill, snow, and endurance races demand the increased traction and mobility of a two-wheel drive bicycle. Conventional bicycles are powered through a chain linking the pedal crankshaft to the rear wheel. Bicyclists are now facing many obstacles where having only rear wheel drive can lead to bicycle damage or personal injury. For professional riders, precious race time is lost avoiding obstacles such as logs, rocks, loose sand, mud, or ice. Traction and climbing ability are severely limited in extreme mountain conditions by only having the rear wheel provide power. In fact, biking professionals teach that only through learning to keep your weight on the rear wheel will beginners ever hope to improve their off-road skills. Accordingly, there is a need in the industry for a two-wheeled drive bicycle which efficiently transfers power from the pedals to the front wheel, provides the rider with increased ability to safely negotiate rough terrain, and which does not detract from the aesthetic qualities and appearances of the bicycle structure itself.
The concept of a two-wheel drive bicycle is not a new one. Several two-wheel drive bicycle systems are patented at present using various combinations of chains, flexible cable shafts, and rocker arms mounted on the handlebars to transfer power either directly from the pedals to the front wheel or from the rear wheel to the front wheel. In general, two-wheel drive bicycles fall into two categories: 1) permanent designs involving drive trains attached to the frame, and 2) retrofit kits which convert existing bicycles to two-wheel drive. The main drawbacks to these systems are: 1) a modification to the standard bicycle in the form of a kit is expensive when considered as an addition to a bicycle purchase, 2) the low strength flexible shaft limits the allowable loading on the system, 3) the retro-fit kit requires considerable skill to attach and cannot be designed to optimally work with every frame design, and 4) the drive mechanisms are often large and openly exposed on the outside of the frame potentially creating additional hazards for the rider and detracting from the overall appearance of the bicycle.
U.S. Pat. No. 4,773,662 shows a bicycle with a front wheel driven by a chain connected to a handle-bar mounted hand pedaling system. The bicycle uses arm power to drive the front wheels and is adaptable to a conventional bicycle frame.
U.S. Pat. No. 5,542,689 shows a front wheel drive system for a bicycle which can be installed on a bicycle to drive the front wheel by rocking the handlebars back and forth. As with U.S. Pat. No. 4,773,662 mentioned previously, this bicycle attempts to harness the energy of the rider""s arms as an additional power source for driving the bicycle. However, a drive mechanism requiring the use of the riders arms for more than steering, balance and control of the vehicle would likely create serious safety problems and interfere with the bicycle operation for both professional and recreational mountain bikers.
U.S. Pat. No. 5,052,705 describes a bicycle with power distribution from the rear wheel to the front wheel via a caliper and cable drive system. The drive system is activated by a caliper clamped on the rear wheel connected by a cable to a caliper on the front wheel. Inefficient power transfer to the front wheel due to slippage as well as torque loss in the cable would be a problem with this system.
U.S. Pat. No. 5,224,725 describes one permanent system that has been developed utilizing a series of chains and sprockets. This design involved many moving parts that would make the bicycle very awkward and difficult to maintain. The exposed chain that runs along the top tube would be hazardous to the rider and the front chain also would interfere with steering.
U.S. Pat. No. 5,324,057 describes a bicycle driven with a chain meshed with both the front and rear sprockets through a plurality of gears, pulleys and spring systems to power the front wheel.
Several two-wheel drive bicycles demonstrate a front wheel driven by flexible cables or flexible cables in combination with chains. (See e.g., U.S. Pat. Nos. 5,332,244, 5,253,889, 5,158,314, 5,116,070, and 4,895,385). The systems, such as the bicycle produced by Turner Drive Systems of Rogers, Arkansas, target the market for a drive system which can be retrofit to any standard frame with modifications primarily to the gearing and chain attachments necessary to drive the front wheel.
As disclosed, U.S. Pat. No. 5,332,244 uses chain-sprocket arrangements, along with a flexible shaft to transmit some of the power from a rear gearbox to the front wheel. The retrofit system utilizes the inner most sprocket for the drive system, however the rider can use the other sprockets to shift gears normally. Deformation of the flexible cable, and corresponding loss of efficient power transfer from the rear wheel to the front wheel is a drawback of each of these systems when compared to the rigid shaft drive of the present invention.
U.S. Pat. No. 5,158,314 uses a complex mechanical system to power the front wheel from the powered rear wheel. A first traction chain coupled to the rear wheel and attached to the frame is connected to a series of rigid and flexible shafts which attach to a second traction chain which is mounted above the front wheel and powers the front wheel. U.S. Pat. Nos. 4,029,332 and 4,474,660 also describe two-wheel drive bicycles with complex chain or belt drive and pulley systems.
Bicycle hubs utilizing roller clutch bearings are described in U.S. Pat. Nos. 5,485,905 and 5,662,197. However, neither application discloses the use of the roller clutch hub to provide power transmission advantages for the front wheel drive of a two-wheel drive bicycle nor does either utilize more than a single roller clutch within the hub for added strength and durability of the hub shell.
It is, therefore, the object of this invention to provide a two-wheel drive bicycle with a front wheel that is powered by a rigid shaft front wheel drive and, therefore, does not experience the loss of power due to slippage or elasticity associated with flexible shafts and other drive systems.
It is a further object of this invention to provide a two-wheel drive bicycle wherein the rigid front wheel drive powers the front and rear wheels simultaneously in a ratio which enables safe and effective operation of the bicycle and provides immediate transfer of power from the pedals to the front wheel.
It is a further object of this invention to construct the bicycle frame in a manner that substantially encloses the front wheel drive within the frame and provides effective two-wheel drive biking with no interference of rider motion, with normal braking and steering radius, and with minimal rider danger with respect to moving parts and obstruction of operation.
It is a further object of this invention to provide a front wheel drive that adapts to a variety of common bicycle frame designs including rear suspension, the xe2x80x9cdouble diamondxe2x80x9d frame configuration found on most mountain, road, touring commuter, comfort, electric and BMX bicycles, as well as the frame configurations of recumbent and tandem bicycles.
It is a further object of this invention to include an engagement clutch that allows the rider the option to choose between rear-wheel-only and two-wheel drive operation when conditions warrant.
It is a further object of this invention to incorporate the front wheel drive technology into a shock-absorbing front fork and rear suspension system of a bicycle to provide the rider with a smoother ride.
It is a further object of this invention to disclose a free wheeling hub for the front wheel that utilizes a roller clutch bearing, and therefore, does not feature a continual ratcheting sound as the bicycle is being operated in the optional rear-wheel-only drive configuration and the front wheel is free wheeling. Additionally, in one embodiment, the free wheeling hub includes a torque-limiting clutch to prevent failure of the front wheel drive.
It is a further object of this invention to disclose alternative drive systems that can be incorporated into the frame of the bicycle to power the front wheel either from the rear wheel or directly from the pedals and crank tube region of the frame. Alternative front wheel drives include ball-bearing drive, hydraulic, or a combination of internal belts, chains, or cables such that the steering radius is unimpeded and there is no significant power loss in transferring power to the front wheel.
Other objects and advantages will be more fully apparent from the following disclosure and appended claims.
The present invention is a two-wheel drive bicycle, otherwise known as an all wheel drive bicycle or a bicycle powered by both the rear and the front wheels simultaneously. The two-wheel drive bicycle disclosed herein may include a shock-absorbing front fork or rear suspension system. Additionally, the front wheel drive of the two-wheel drive bicycle is adapted to a number of bicycle frame configurations including double diamond frames found on mountain, road, BMX, electric, commuter, touring, comfort and other common bicycle models as well as adaptation of the front wheel drive to recumbent and tandem bicycles. The front wheel drive as disclosed herein can power the front wheel from gears located at the rear wheel or from gears located at an automatic transmission located within or near the crank tube of the frame. The front wheel drive may include rigid shafts and meshing gears or a number of other drive components and assemblies, including hydraulic and ball bearing drives, that are internalized within the bicycle frame and that minimize power loss when powering the rear wheel without limiting the steering range. A two-wheel drive bicycle provides a rider increased safety and the ability to significantly increase speed during navigation through dangerous stretches of terrain.
The present invention, as described in the first through seventeenth embodiments, has several objectives. A first is to provide a two-wheel drive bicycle using a rigid shaft drive as the main power transfer means to the front wheel. Rigid shafts have the advantage of virtually instantaneous power transfer, whereas flexible shafts usually have from 10 to 20 degrees of rotation displacement when applied with a torque which would lead to a spongy feeling when pedaling the bicycle.
Essentially, the rider could turn the pedal several inches before the front wheel would begin to turn. Additionally, a rigid shaft drive is supported by bearings which results in very low friction in the front wheel drive. Alternatively, a front wheel drive that provides virtually instantaneous power transfer without rotation displacement would be acceptable substitutes for the rigid shafts of the front wheel drive. More specifically, ball bearing drives, hydraulic drives, internalized cables, chains, belts, or a combination thereof, could be utilized. In each such case, the important feature is that the front wheel is instantaneously driven when power is applied to the rear wheel without loss of power, increased drive system friction, or the rider noticing a spongy feeling when transferring power through the front wheel drive.
Secondly, the front wheel drive of the two-wheel drive bicycle is substantially incorporated into the frame. Alternatively, the front wheel drive should be enclosed in a tube which is attached to the frame. The primary reason for enclosing the front wheel drive is to maintain the front wheel drive in a fixed position thereby minimizing or eliminating slippage and, as importantly, enclosing the moving parts to minimize danger to the rider. Enclosing the front wheel drive will also avoid the costly, time consuming and often bulky modifications necessitated in configuring the retrofit two-wheel drive models while also maintaining the general aesthetic appearance of a standard bicycle. Importantly, enclosing the front wheel drive in the frame within, near, or proximate the head tube also places front wheel drive components on the axis of steering to minimize torque reactions from the rotating components. Finally, enclosing the front wheel drive within the frame enables adaptation to numerous common bicycle frame designs including full suspension, xe2x80x9cdouble diamond,xe2x80x9d touring or comfort bicycles, recumbent, and tandem bicycles.
Third, both the front and back wheel of the two-wheel drive bicycle are designed to accommodate a system of sprockets or bevel gears. The rear wheel transmits torque to the front wheel drive through the shaft either by using a power transfer mechanism at the rear wheel comprising, for example, a bevel gear mounted on the rear drive sprocket set which s directly interacts with the pinion gear on the drive shaft. The power is transferred from the drive shaft to the front wheel by a pinion gear engaging with a bevel gear mounted on the axle of the front wheel. The gears may feature either straight or helical (spiral) gear teeth. Alternatively, the front wheel drive can originate directly from the crank tube area of the frame. In that configuration, a manual or automatic transmission within the crank tube would transfer power to the rear wheel with a direct drive shaft or chain and a second drive shaft would exit the transmission toward the front wheel of the bicycle to provide power to the front wheel.
Fourth, the neck and head tubes of the bicycle frame are designed to accommodate a pair of meshing gears with one being attached to the front end of the main drive shaft and the other being attached to the top end of the front drive shaft which descends to the front wheel. The head and neck tubes, which may be either standard sized or enlarged, are necessary to enable the miter gears to mesh at an angle of 90 degrees or less while enabling an optimum head tube angle relative to the ground for steering responsiveness. Furthermore, the head and neck tubes should be modified to enable an adequate turning radius of the front wheel of approximately 180 degrees.
In the present invention, the neck tube is preferably cut away in the center to accommodate the meshing gears and is then supported within the head tube by attaching at the top and bottom ends to the front fork. The severed neck tube forms an upper neck tube section and a lower neck tube section and is then further supported by bearings within the head tube and attached at each end to the front fork to enable adequate turning radius and front fork strength. In bicycles that do not feature a traditional head and neck tube design, such as the four-bar linkage front suspension disclosed herein, the front wheel drive exits the frame proximate the axis of steering immediately behind the steering mechanism to permit the full steering range while minimizing unwanted torque reactions from the rotating front wheel drive. Finally, where the front wheel drive originates within the crank tube, similar designs enable negotiation through the head and neck tubes.
Fifth, the frame of the bicycle is modified into a split configuration to enable a straight path for the drive shaft from the rear of the bike to the head and neck tubes. However, any frame configuration which substantially incorporates the rigid drive shaft into the frame from the vicinity of the rear wheel to the head tube and down the front fork assembly of the bicycle is envisioned. Incorporating the front wheel drive within the frame enables adaptation of the front wheel drive to numerous common bicycle frame designs including full suspension, xe2x80x9cdouble diamond,xe2x80x9d comfort, touring, commuter bikes, road, BMX, electric and even recumbent or tandem bicycles. Two-wheel drive versions of recumbent and tandem bicycles would provide the rider added control in wet or loose conditions. An additional advantage for recumbent or tandem bicycles, as disclosed in the invention, is the use of shafts in place of lengthy chains for certain portions of the drive train. Standard recumbent bicycles utilize a lengthy chain from the pedals in the front of the bicycle to the rear wheel which is usually behind the rider. The use of a shaft drive to the front wheel, and then as a substitute for a portion of the lengthy drive chain, will provide the rider a safer ride and result in less broken and skipping chains.
Sixth, the drive shaft descending from the neck of the bicycle to the front axle should be configured to enable both free motion in the steering of the bicycle and free rotation of the front tire as well as no interference with braking. In the embodiments disclosed herein, a pair of universal joints are used to negotiate clearance by the rigid shafts around the front wheel. Alternatives to using standard universal joints with pins include ball spline universal joints or other well-known linkages. An alternative front fork design completely encloses the drive shaft and universal joint within one of the front fork members as shown in the eighth and ninth embodiments. In this configuration, a universal joint could be enclosed within the fork crown, or alternatively, a series of meshing gears within the fork crown could be used to enable adequate clearance for the front wheel drive to avoid interference with the front wheel.
Other mechanisms and gear combinations are also envisioned and the front wheel drive may also contain an adjustable component to enable the compression of the front fork or movement of the rear wheel in a rear-suspension system bicycle. One such alternate combination, as described in the third embodiment, is an expandable universal joint system with a pair of sliding shafts that adjusts with the expansion and compression of a shock-absorbing front fork while maintaining power transmission to the front wheel. Alternatively, as discussed in the fourth, eighth and ninth embodiments, sliding shafts along the fork member or a sliding shaft within one of the meshing gears located within the fork crown could be utilized to accommodate the expansion and contraction of the shock-absorbing front fork instead of a telescoping universal joint. Also, as disclosed in the fifth embodiment, alternate drive components can be used instead of the miter gears for transmitting power from the main drive shaft to the front drive shaft system.
Seventh, the front wheel drive includes an engagement clutch located at the rear wheel to enable the rider to optionally shift the bicycle from rear-wheel-only drive to two-wheel drive. The engagement clutch for the front wheel drive is preferably a cable-activated clutch featuring engaging dog tooth plates that mounts on standard disk brake bicycle hubs. Accordingly, the narrow dimensions and diameter of the clutch are essential to incorporating this feature into the front wheel drive while maintaining the ability to utilize standard bicycle components and frame spacing.
Eighth, free wheeling or one-way front and rear hubs utilizing roller clutches are disclosed. The roller clutch has the added advantages of being both silent in its operation and virtually instantaneous in engaging as the one-way hub reverses from its free-wheeling direction to the engaged direction. The free wheeling hub disclosed herein also features a torque limiting clutch to prevent front wheel drive failure upon the transfer of severe torque loads through the drive system.
Ninth, a torque limiting clutch is disclosed that enables the front wheel drive to rotate independently from the front wheel when extreme torque loads are transmitted to the front wheel. Accordingly, torque loads that may cause failure to the front wheel drive can be relieved by the torque limiting clutch without damage to the front wheel drive.
Thus, according to the broad aspects of the invention, the two-wheel drive bicycle comprises:
(a) a rigid front wheel drive that transmits power from the rear wheel to the front wheel, or from the crank tube to the front wheel, through a series of rigid drive shafts including a main drive shaft and a front drive shaft and a series of meshing gears or, alternatively, through other front wheel drive configurations such as ball bearing and hydraulics that would efficiently and instantaneously transmit power to the front wheel with minimal power loss due to drive system friction and without a xe2x80x9cspongyxe2x80x9d pedaling sensation;
(b) a frame constructed of tubing, including sections which enclose the front wheel drive system and which is integral with or a part of the bicycle frame;
(c) a neck tube and a head tube designed to accommodate the drive shaft system in a manner that maintains optimum head angle and permits an adequate turning radius;
(e) a front drive shaft system descending to the front wheel configured to enable both free motion in the steering of the bicycle and free rotation of the front wheel without interfering with braking or tire rotation;
(f) a shock-absorbing front fork and a rear suspension system that incorporate the front wheel drive to ensure a smoother ride;
(g) An engagement clutch to provide the rider the option of shifting the bicycle from two-wheel drive to rear wheel-only drive;
(h) A one-way hub utilizing a roller clutch for silent rotation and resulting in minimal backlash in both the front and rear wheels;
(i) A torque-limiting clutch to enable release of extreme torque loads within the front drive prior to failure.
In summary, in the present invention, the power is transferred from the pedals to the front wheel through a rigid front wheel drive shaft system including a series of meshing gears. The frame of the bicycle is designed to contain the front wheel drive system that transmits power to the front wheel. In order to have a straight path from the rear wheel to the neck tube, the main frame tube is split into two tubes that run directly from the neck to a gear mounted on the rear wheel. Alternative frame configurations are possible through the utilization of universal joints, ball spline universal joints, or other front wheel drive pivot points at certain points in the frame. The front wheel drive system may also originate from within the crank tube of the bicycle frame directly to the front wheel.
The power is transmitted from the rear wheel wherein the drive gear at the end of the drive shaft meshes with a bevel gear mounted circumferentially on the rear drive gears. At the front end, the main drive shaft connects to a gear that is located inside the front head tube of the bicycle and meshes with a second gear. The neck and head tube are standard-sized or, alternatively, enlarged in comparison to a standard bicycle to allow for full steering capabilities of the bicycle while transferring power to the front wheel. The gears as shown are connected to one or more standard universal joints or ball spline universal joints that are then connected to a front rigid drive shaft system. The purpose of this configuration is to allow the rigid front shaft system to negotiate around the front tire and to allow free motion of the wheel for both rotation and steering. Alternative configurations which would ensure that the front drive shaft does not interfere with steering or rotation of the front wheel are also anticipated. One such alternative would reduce the number of components to a single front drive shaft angled from the head tube to the front hub. Another such alternative would utilize a single piece composed of a pair of interconnected universal joints of appropriate length with the miter gear at one end and the front drive shaft at the other end. Additionally, a series of meshing gears completely contained within the fork crown could be utilized. In addition, alternate drive components can be used instead of the miter gears for transmitting power from the main drive shaft to the front drive shaft system. Those skilled in the art will recognize other methods for constructing a front drive shaft system which does not interfere with the front wheel, and the embodiments disclosed herein are not to be construed as limiting.
The front drive shaft transmits power to the front wheel through the interface of a pinion gear attached to the lower end of the front shaft and a bevel gear mounted circumferentially on the front wheel hub. The front wheel hub should be a one-way hub which catches in one direction but freewheels in the other direction to enable the rider to coast without the pedals turning. The front wheel hub could utilize a roller clutch to enable one-way freewheeling. Roller clutches have the added advantage of silent operation and nearly instantaneous engagement. While virtually all ratcheting hubs feature some degree of backlash as the ratchet engages, the roller clutch engages virtually as soon as the rotational direction of the hub changes. This feature is important for the front wheel drive so that any power transferred through the front wheel drive will result in instantaneous front wheel traction whereas the use of a ratcheting front hub would result in some degree of rotational backlash in the front hub before the front wheel would engage and become powered by the front wheel drive. Additionally, the use of at least two roller clutches within a single rear hub would provide additional strength in the system by spreading the torque forces over a larger surface within the hub shell.
As disclosed, a shock-absorbing front fork is incorporated into the bicycle design of the present invention. The expandable universal joint system includes a middle section with an inner sliding shaft and an outer sliding shaft that increases and decreases the distance between the universal joints as the shock-absorbing front fork expands and shortens in length. Additionally, the shock-absorbing front fork is connected to a neck tube that incorporates the features as disclosed herein, including but not limited to a cutout section or completely severed neck tube which enables rotation around the meshing gears providing adequate steering rotation. Alternative front fork designs include the use of ball spline universal joints in the place of standard pin universal joints and the complete integration of the front wheel drive within the front fork crown and fork members. Those skilled in the art will recognize other methods for constructing and mounting a shock-absorbing front fork onto the bicycle frame in a manner which does not interfere with steering or rotation of the front wheel while enabling the front drive shaft system to expand and to contract with the expansion and contraction of the shock-absorbing front fork.
In general, the disclosed front wheel drive assembly could be utilized similarly in any two-wheel drive two-wheeled vehicle including motorcycles, mopeds, and pedal assist vehicles. The relevant concepts for a two-wheel drive motorcycle would involve the transfer of the power from the rear wheel (as in the second and sixth embodiments) or the center drive transmission (as in the eleventh embodiment) through a rigid drive system, internal to the motorcycle frame to enable a full range of steering and instantaneous power transfer to the front wheel. Furthermore, front wheel drive components located symmetrically and along the axis of steering are important to controlling torque reactions. Like a two-wheel drive bicycle, the two-wheel drive motorcycle would have increased traction and mobility of the front wheel, especially during uphill climbs and downhill cornering on loose or slippery material. The shock-absorbing front fork and rear suspension ensures a smoother ride and greater contact of the front wheel with the terrain for all-around improved rider experience. The invention discloses a method of manufacturing a functional two-wheel drive two-wheeled vehicle with all the disclosed embodiments. As envisioned, this fully integrated front wheel drive would not only compete with the most advanced two-wheeled vehicles on the market but would also create an entirely new category in numerous industries.